Combined effects of octenylsuccination and oregano essential oil on sweet potato starch films with an emphasis on water resistance.

The perishable character of moist food products demands packages with antimicrobial activity and water resistance. Oregano essential oil (OEO) and starch octenylsuccination were first jointly applied to formulate antimicrobial and water-resistant sweet potato starch films. The results showed that octenylsuccination powerfully retarded the coalescence of oil droplets in film casting process and favoured their homogeneity in the dried films. OEO incorporation dose-dependently conferred antimicrobial activity upon the films, which was further enhanced by octenylsuccination to some degree. For a specific film, comparable inhibitory efficacies were observed against S. aureus and E. coli. Either octenylsuccination or OEO incorporation alone decreased film strength, rigidity, water content, water solubility and water vapor permeability while increasing film extensibility to a less degree than their combination. More importantly, synergistic effects between OEO incorporation and octenylsuccination were concluded on film water content, water solubility and extensibility.